The intense heat wave that gripped Siberia during the first half of 2020 would have been impossible without human-caused climate change, a new study finds. Researchers with the World Weather Attribution Network report that climate change made the prolonged heat in the region at least 600 times more likely — and possibly as much as 99,000 times more likely.

“We wouldn’t expect the natural world to generate [such a heat wave] in anything less than 800,000 years or so,” climate scientist Andrew Ciavarella of the U.K. Met Office in Exeter, England, said July 14 in a news conference. It’s “effectively impossible without human influence.”

The new study, posted online July 15, examined two aspects of the heat wave: the persistence and intensity of average temperatures across Siberia from January to June 2020; and daily maximum temperatures during June 2020 in the remote Siberian town of Verkhoyansk.

Tiny Verkhoyansk made international headlines when it logged a record high temperature of 38° Celsius (100.4° Fahrenheit) on June 20 (SN: 6/23/20). The record was just one extreme amid a larger and longer event in the region that has led to a series of human and natural disasters (SN: 7/1/20). Those include wildfires across Siberia, the collapse of a fuel tank in the mining city of Norilsk due to sagging permafrost, and heat health effects (SN: 4/3/18).

Using observational data from Verkhoyansk and other Siberian weather stations, the researchers first assessed the rarity of the observed temperatures and determined temperature trends. Then they compared these observations with hundreds of climate simulations using different greenhouse gas warming scenarios. 

Had such a hot spell occurred in 1900 instead of 2020, it would have been at least 2 degrees cooler on average, the researchers found. In Verkhoyansk, climate change amped up June temperatures by at least 1 degree relative to 1900. And such heat waves are likely to become more common in the near future, the scientists found: By 2050, temperatures in Siberia could increase by between 2.5 degrees to as much as 7 degrees compared to the year 1900, the report finds.